Development of new neurologic studies requires thorough historic and methodologic reviews of prior investigations. These yielded important unexplored etiologic clues that may be investigated using current technology. Major emphasis has been given to: cerebrovascular disease; otitis media; inherited ataxias; Huntington's disease; febrile seizures; Tourette's syndrome; peripheral neuropathy; neurologic disease in the elderly; controlled therapeutic trials of motor neuron disease; epilepsy; descriptive, analytic, and experimental methods in neuroepidemiology; procedures for neuroepidemiologic investigations in developing countries; and epidemiologic studies of Alzheimer's disease, myasthenia gravis, cerebral malaria, and autism.